Why was Booth admitted into the presidential box?

[RJNorton]

Here is the way Theodore Roscoe put it in The Web of Conspiracy:

"Arrest an English actress who had been on the stage with Booth, yes. Arrest a young lady who had chatted with Booth in the parlor of a boardinghouse. Arrest and imprison a backwoods farmer's wife who had served a dish of tea to a caller who might have been Booth. Arrest and imprison a scullery maid who had cried, "Hoo-ray for Booth." But do not arrest the society woman who had consorted with him in Washington drawing-rooms. Do not impound this amourette who seated the killer near Lincoln at the Inaugural. Never breathe the name of Booth's betrothed. She is privileged, beyond the law, sacrosanct. She is the daughter of a United States Senator!"